1. Field of the Invention
The present invention relates to a rear wheel steering apparatus for a four-wheel steering vehicle.
2. Description of the Prior Art
A four-wheel steering vehicle is such a vehicle that whenever the front wheels are steered, an actuator is actuated to steer the rear wheels simultaneously.
FIG. 5 shows an example of a prior art rear wheel steering apparatus which is disclosed in Utility Model Laid Open Publication application Ser. No. 145773/1989. In FIG. 5, a pair of right and left steering axles 51R and 51L are pivotally supported on a fixed frame 50 via bearings. The steering axles 51R and 51L are formed with right and left levers 52R and 52L, respectively. Ends of these two levers 52R and 52L are linked with each other by a connecting rod 53. Further, the steering axles 51R and 51L are provided with right and left eccentric pins 54R and 54L, respectively. Right and left suspension links 55R and 55L are connected to the eccentric pins 54R, 54L via pins, respectively. Further, the lever 52R is connected to an output shaft of a motor 56.
In operation, when a rear wheel steering command signal is applied from a controller (not shown) to the motor 56, the right and left steering axles 51R and 51L are pivoted by the motor 56, respectively in synchronism with each other. Therefore, the right and left eccentric pins 54R and 54L are pivoted by a predetermined angle, so that the right and left suspension links 55R and 55L are shifted in the right and left directions, respectively to steer the rear right and left wheels, respectively.
In the above-mentioned rear wheel steering apparatus, however, there exist some problems in that it is rather difficult to secure high precision uniformly on the right and left sides in processing and in assembly of the eccentric pins 54R and 54L, the levers 52R and 52L, the suspension links 55R and 55L, the connecting rod 53, etc. In addition the productivity is low because a relatively large cast casing (not shown) for housing and supporting these elements is required. Further, there exists another problem in that a large space is required to mount the connecting rod 53, because the connecting rod 53 is inevitably oscillated up and down.